The invention relates to an electronic control unit with triggering and power components, in particular an ignition control unit, whose circuit includes various subassemblies formed in hybrid technique.
Electronic ignition circuits, for example for automotive applications, consist of various parts or subassemblies, which are each assembled on a reseptive ceramic carrier as a hybrid circuit. A control unit, a switching element and an RC combination are usually required for this application.
The control unit, which serves to trigger and control the switching element, is built up on a ceramic substrate with printed conductor lines and resistors, by use of components in SMD- and chip form. The switching element represents the circuit breaker that switches the ignition coil current on and off in ignition control units. It comprises, for example, a power transistor chip soldered onto a metallic heat spreader used to improve the removal of dissipated power.
The RC combination contains a ceramic high-voltage capacitor and a power resistor. In ignition control units these components are either installed discretely in the plastic frame of the housing, or are mounted on a separate ceramic substrate which contains a printed power resistor and a high-voltage capacitor.
The dissipated power of the control unit is small compared with the power dissipation of the switching element. The dissipated power has to be removed to a heat sink.
For the electrical insulation of the control unit and of the switching element to heat sink, both of them are built up on a metallized ceramic substrate and mounted singly onto the heat sink. The electrical connection of the components to each other is made by Al-wire bonds.
An ignition control unit whose circuit components are deposited on an AlN ceramic carrier is known from German patent DE-PS 36 04 074.
However, the AlN ceramic carrier material is very expensive; in addition, the mechanically stabilizing heat sink is not present, so that the system is prone to breakage when fitted in the vehicle.